Customized patient-specific orthopaedic pin guides

ABSTRACT

Customized patient-specific orthopaedic surgical instruments are disclosed. Methods for fabricating and using such instruments are also disclosed.

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 14/155,656, which was filed on Jan. 15, 2014, whichis a continuation of and claims priority to U.S. patent application Ser.No. 13/173,880, which was filed on Jun. 30, 2011 and issued as U.S. Pat.No. 8,641,721 on Feb. 4, 2014, and is expressly incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates generally to customized patient-specificorthopaedic surgical instruments, and in particular to customizedpatient-specific orthopaedic pin guides.

BACKGROUND

Joint arthroplasty is a well-known surgical procedure by which adiseased and/or damaged natural joint is replaced by a prosthetic joint.A typical knee prosthesis includes a tibial tray, a femoral component, apolymer insert or bearing positioned between the tibial tray and thefemoral component, and, in some cases, a polymer patella button. Tofacilitate the replacement of the natural joint with the kneeprosthesis, orthopaedic surgeons use a variety of orthopaedic surgicalinstruments such as, for example, cutting blocks, drill guides, millingguides, and other surgical instruments. Typically, the orthopaedicsurgical instruments are generic with respect to the patient such thatthe same orthopaedic surgical instrument may be used on a number ofdifferent patients during similar orthopaedic surgical procedures.

SUMMARY

According to one aspect, a customized patient-specific orthopaedicsurgical instrument includes a customized patient-specific tibial pinguide. The pin guide includes a body having a bone-facing surface thathas a customized patient-specific negative contour configured to receivea portion of an anterior side of a patient's tibia that has acorresponding positive contour. The body has a first hole formed thereinwith a first locking slot extending in a direction parallel to the axisof the first hole. The first locking slot opens into the first hole. Thebody also has a second hole formed therein with a second locking slotextending in a direction parallel to the axis of the second hole. Thesecond locking slot opens into the second hole. The customizedpatient-specific tibial pin guide also has a first tab extendingposteriorly from the body. The first tab has a bone-facing surface thathas a customized patient-specific negative contour configured to receivea first portion of the proximal side of the patient's tibia that has acorresponding positive contour. The customized patient-specific tibialpin guide also has a second tab extending posteriorly from the body, thesecond tab including a bone-facing surface that has a customizedpatient-specific negative contour configured to receive a second portionof the proximal side of the patient's tibia that has a correspondingpositive contour. The customized patient-specific orthopaedic surgicalinstrument also includes a first removable drill bushing having a postwith a locking flange extending therefrom. The post of the firstremovable drill bushing is positioned in the first hole of the body ofthe customized patient-specific tibial pin guide such that the lockingflange of the first removable drill bushing is positioned in the firstlocking slot of the body of the customized patient-specific tibial pinguide. The customized patient-specific orthopaedic surgical instrumentfurther includes a second removable drill bushing having a post with alocking flange extending therefrom. The post of the second removabledrill bushing is positioned in the second hole of the body of thecustomized patient-specific tibial pin guide such that the lockingflange of the second removable drill bushing is positioned in the secondlocking slot of the body of the customized patient-specific tibial pinguide.

The locking slots of the customized patient-specific tibial pin guidemay be embodied as female threads extending helically around theperiphery of the holes of the customized patient-specific tibial pinguide, with the locking flanges of the removable drill bushings beingembodied as male threads extending helically around the post of theremovable drill bushings. The male threads of the drill bushings arethreaded into the female threads of the body so as to lock the removabledrill bushings to the customized patient-specific tibial pin guide.

In an embodiment, an outer end of each of the locking slots opens intoan outer surface of the body of the customized patient-specific tibialpin guide that is opposite the bone-facing surface, with an inner end ofeach of the locking slots defining an annular recess formed in the bodyof the customized patient-specific tibial pin guide. The locking flangesof the removable drill bushings may include a tab that extends outwardlyfrom the post of the removable drill bushings, with such a tab beingcaptured in the annular recess so as to lock the removable drill bushingto the customized patient-specific tibial pin guide.

The customized patient-specific orthopaedic tibial pin guide may beformed from a polymeric material, with both the first removable drillbushing and the second removable drill bushing being formed from ametallic material.

The body, the first tab, and the second tab of the customizedpatient-specific tibial pin guide may define a monolithic structure.

The body, the first tab, and the second tab of the customizedpatient-specific tibial pin guide may define a disposable monolithicstructure.

The body, the first tab, and the second tab of the customizedpatient-specific tibial pin guide define a monolithic, disposablepolymeric structure, with both the first removable drill bushing and thesecond removable drill bushing being reusable and formed from a metallicmaterial.

The first tab and the second tab of the customized patient-specifictibial pin guide may define an opening therebetween.

The first removable drill bushing and the second removable drill bushingare positioned to allow a surgeon to install a pair of guide pins on theanterior side of the patient's tibia.

According to another aspect, a customized patient-specific orthopaedicsurgical instrument includes a customized patient-specific femoral pinguide. The pin guide has a body that includes a bone-facing surface thathas a customized patient-specific negative contour configured to receivea portion of an anterior side of a patient's femur that has acorresponding positive contour. The body has a first hole formed thereinwith a first locking slot extending in a direction parallel to the axisof the first hole. The first locking slot opens into the first hole. Thebody also has a second hole formed therein with a second locking slotextending in a direction parallel to the axis of the second hole. Thesecond locking slot opens into the second hole. The customizedpatient-specific femoral pin guide also has a first tab extendingposteriorly from the body. The first tab has a bone-facing surface thatincludes a customized patient-specific negative contour configured toreceive a first portion of the distal side of the patient's femur thathas a corresponding positive contour. The first tab has a third holeformed therein with a third locking slot extending in a directionparallel to the axis of the third hole. The third locking slot opensinto the third hole. The customized patient-specific femoral pin guidealso includes a second tab extending posteriorly from the body. Thesecond tab has a bone-facing surface that includes a customizedpatient-specific negative contour configured to receive a second portionof the distal side of the patient's femur that has a correspondingpositive contour. The second tab has a fourth hole formed therein with afourth locking slot extending in a direction parallel to the axis of thefourth hole. The fourth locking slot opens into the fourth hole. Thecustomized patient-specific orthopaedic surgical instrument alsoincludes a first removable drill bushing having a post locked into thefirst hole. The customized patient-specific orthopaedic surgicalinstrument further includes a second removable drill bushing having apost locked into the second hole. The customized patient-specificorthopaedic surgical instrument includes a third removable drill bushinghaving a post locked into the third hole. And finally, the customizedpatient-specific orthopaedic surgical instrument includes a fourthremovable drill bushing having a post locked into the fourth hole.

The locking slots of the customized patient-specific femoral pin guidemay be embodied as female threads extending helically around theperiphery of the holes of the customized patient-specific femoral pinguide, with the locking flanges of the removable drill bushings beingembodied as male threads extending helically around the posts of theremovable drill bushings. The male threads of the drill bushings arethreaded into the female threads of the pin guide so as to lock theremovable drill bushings to the customized patient-specific femoral pinguide.

In an embodiment, an outer end of each of the locking slots opens intoan outer surface of the customized patient-specific femoral pin guidethat is opposite the bone-facing surface, with an inner end of thelocking slots defining an annular recess formed in the customizedpatient-specific femoral pin guide. The locking flanges of the removabledrill bushings may include a tab that extends outwardly from the post ofthe removable drill bushings, with such a tab being captured in theannular recess so as to lock the removable drill bushing to thecustomized patient-specific femoral pin guide.

The body, the first tab, and the second tab of the customizedpatient-specific femoral pin guide may be formed from a polymericmaterial, with each of the first, second, third, and fourth removabledrill bushings being formed from a metallic material.

The body, the first tab, and the second tab of the customizedpatient-specific femoral pin guide may define a monolithic structure.

The body, the first tab, and the second tab of the customizedpatient-specific femoral pin guide may define a disposable monolithicstructure.

The body, the first tab, and the second tab of the customizedpatient-specific femoral pin guide may define a monolithic, disposablepolymeric structure, with each of the first, second, third, and fourthremovable drill bushings being reusable and formed from a metallicmaterial.

The first tab and the second tab of the customized patient-specificfemoral pin guide may define an opening therebetween.

The first removable drill bushing and the second removable drill bushingmay be positioned to allow a surgeon to install a first pair of guidepins on the anterior side of the patient's tibia, with the thirdremovable drill bushing and the fourth removable drill bushing beingpositioned to allow a surgeon to install a second pair of guide pins onthe distal side of the patient's tibia.

According to another aspect, a method of performing an orthopaedicsurgical procedure on a bone of a patient includes assembling acustomized patient-specific pin guide assembly by locking a firstremovable drill bushing into a first hole of a customizedpatient-specific pin guide and then locking a second removable drillbushing into a second hole of the customized patient-specific pin guide.The assembled customized patient-specific pin guide assembly is thenpositioned in contact with the bone of the patient. A pair of guide pinsis inserted into the bone of the patient by advancing a first guide pinof the pair of guide pins through the first removable drill bushing, andthen advancing a second guide pin of the pair of guide pins through thesecond removable drill bushing. The customized patient-specific pinguide assembly is then removed from the bone of the patient withoutremoving the pair of guide pins from the bone of the patient. Apatient-universal cutting block is then positioned into contact with thebone of the patient such that the pair of guide pins is received into apair of guide pin holes defined in the patient-universal cutting block.A cut is then made in the bone of the patient with the patient-universalcutting block.

The customized patient-specific pin guide assembly may be disassembledby unlocking the first removable drill bushing from the first hole ofthe customized patient-specific pin guide, and then unlocking the secondremovable drill bushing from the second hole of the customizedpatient-specific pin guide. The disassembled customized patient-specificpin guide assembly may be removed from the bone of the patient withoutremoving the pair of guide pins from the bone of the patient.

The patient-universal cutting block may be removed from the bone of thepatient prior to making the cut in the bone of the patient, andthereafter repositioned into contact with the bone of the patient suchthat the pair of guide pins is received into a second, different pair ofguide pin holes defined in the patient-universal cutting block prior tomaking the cut in the bone of the patient. In doing so, an amount ofbone to be removed from the bone of the patient may be determinedsubsequent to initially positioning the patient-universal cutting blockinto contact with the bone of the patient. The pair of second, differentguide pin holes which corresponds to the amount of bone to be removedfrom the bone of the patient is then selected from a plurality of pairsof guide pin holes, and the patient-universal cutting block repositionedinto contact with the bone of the patient such that the pair of guidepins is received into the selected second, different pair of guide pinholes defined in the patient-universal cutting block prior to making thecut in the bone of the patient.

The assembled customized patient-specific pin guide assembly may beembodied as a femoral pin guide.

The assembled customized patient-specific pin guide assembly may beembodied as a tibial pin guide.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a simplified flow diagram of an algorithm for designing andfabricating a customized patient-specific orthopaedic surgicalinstrument;

FIG. 2 is a simplified flow diagram of a method for generating a modelof a patient-specific orthopaedic instrument;

FIG. 3 is a simplified flow diagram of a method for scaling a referencecontour;

FIGS. 4-6 are three-dimensional model's of a patient's tibia;

FIG. 7-9 are three-dimensional models of a patient's femur;

FIG. 10 is an anterior elevation view of a customized patient-specifictibial pin guide;

FIG. 11 is a cross section view of the customized patient-specifictibial pin guide taken along the line 11-11 of FIG. 10, as viewed in thedirection of the arrows;

FIG. 12 is a cross section view of the customized patient-specifictibial pin guide taken along the line 12-12 of FIG. 10, as viewed in thedirection of the arrows;

FIG. 13 is a perspective view of a removable drill bushing;

FIG. 14 is an elevation view of the removable drill bushing of FIG. 13;

FIG. 15 is a cross section view of the removable drill bushing of FIG.13;

FIGS. 16-20 show the customized patient-specific tibial pin guide ofFIG. 10 being used to surgically resect the tibia of a patient;

FIG. 21 is a perspective view of a customized patient-specific femoralpin guide;

FIG. 22 is a side elevation view of the customized patient-specificfemoral pin guide of FIG. 21;

FIG. 23 shows the customized patient-specific femoral pin guide of FIG.21 coupled to the femur of a patient;

FIG. 24 is an anterior elevation view of another embodiment of acustomized patient-specific tibial pin guide;

FIG. 25 is a cross section view of the customized patient-specifictibial pin guide taken along the line 25-25 of FIG. 24, as viewed in thedirection of the arrows;

FIG. 26 is a perspective view of another embodiment of a removable drillbushing; and

FIG. 27 is a cross section view of the removable drill bushing of FIG.26.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

Terms representing anatomical references, such as anterior, posterior,medial, lateral, superior, inferior, etcetera, may be used throughoutthis disclosure in reference to the orthopaedic implants and instrumentsdescribed herein, along with a patient's natural anatomy. Such termshave well-understood meanings in both the study of anatomy and the fieldof orthopaedics. Use of such anatomical reference terms in thespecification and claims is intended to be consistent with theirwell-understood meanings unless noted otherwise.

Referring to FIG. 1, an algorithm 10 for fabricating a customizedpatient-specific orthopaedic surgical instrument is illustrated. What ismeant herein by the term “customized patient-specific orthopaedicsurgical instrument” is a surgical tool for use by a surgeon inperforming an orthopaedic surgical procedure that is intended, andconfigured, for use on a particular patient. As such, it should beappreciated that, as used herein, the term “customized patient-specificorthopaedic surgical instrument” is distinct from standard, non-patientspecific orthopaedic surgical instruments (i.e., “patient-universalinstruments” such as patient-universal cutting blocks) that are intendedfor use on a variety of different patients and were not fabricated orcustomized to any particular patient. Additionally, it should beappreciated that, as used herein, the term “customized patient-specificorthopaedic surgical instrument” is distinct from orthopaedicprostheses, whether patient-specific or generic, which are surgicallyimplanted in the body of the patient. Rather, customizedpatient-specific orthopaedic surgical instruments are used by anorthopaedic surgeon to assist in the implantation of orthopaedicprostheses. Examples of “customized patient-specific orthopaedicsurgical instruments” include customized patient-specific drill/pinguides, customized patient-specific tibial cutting blocks, andcustomized patient-specific femoral cutting blocks.

In some embodiments, the customized patient-specific orthopaedicsurgical instrument may be customized to the particular patient based onthe location at which the instrument is to be coupled to one or morebones of the patient, such as the femur and/or tibia. For example, insome embodiments, the customized patient-specific orthopaedic surgicalinstrument may include a bone-contacting or facing surface having anegative contour that matches or substantially matches the contour of aportion of the relevant bone of the patient. As such, the customizedpatient-specific orthopaedic surgical instrument is configured to becoupled to the bone of a patient in a unique location and position withrespect to the patient's bone. That is, the negative contour of thebone-contacting surface is configured to receive the matching contoursurface of the portion of the patient's bone. As such, the orthopaedicsurgeon's guesswork and/or intra-operative decision-making with respectto the placement of the orthopaedic surgical instrument are reduced. Forexample, the orthopaedic surgeon may not be required to locate landmarksof the patient's bone to facilitate the placement of the orthopaedicsurgical instrument, which typically requires some amount of estimationon part of the surgeon. Rather, the orthopaedic surgeon may simplycouple the customized patient-specific orthopaedic surgical instrumenton the bone or bones of the patient in the unique location. When socoupled, the cutting plane, drilling/pinning holes, milling holes,and/or other guides are defined in the proper location relative to thebone and intended orthopaedic prosthesis. The customizedpatient-specific orthopaedic surgical instrument may be embodied as anytype of orthopaedic surgical instrument such as, for example, abone-cutting block, a drilling/pin guide, a milling guide, or other typeof orthopaedic surgical instrument configured to be coupled to a bone ofa patient.

As shown in FIG. 1, the algorithm 10 includes process steps 12 and 14,in which an orthopaedic surgeon performs pre-operative planning of theorthopaedic surgical procedure to be performed on a patient. The processsteps 12 and 14 may be performed in any order or contemporaneously witheach other. In process step 12, a number of medical images of therelevant bony anatomy or joint of the patient are generated. To do so,the orthopaedic surgeon or other healthcare provider may operate animaging system to generate the medical images. The medical images may beembodied as any number and type of medical images capable of being usedto generate a three-dimensional rendered model of the patient's bonyanatomy or relevant joint. For example, the medical images may beembodied as any number of computed tomography (CT) images, magneticresonance imaging (MRI) images, or other three-dimensional medicalimages. Additionally or alternatively, as discussed in more detail belowin regard to process step 18, the medical images may be embodied as anumber of X-ray images or other two-dimensional images from which athree-dimensional rendered model of the patient's relevant bony anatomymay be generated. Additionally, in some embodiments, the medical imagemay be enhanced with a contrast agent designed to highlight thecartilage surface of the patient's knee joint.

In process step 14, the orthopaedic surgeon may determine any additionalpre-operative constraint data. The constraint data may be based on theorthopaedic surgeon's preferences, preferences of the patient,anatomical aspects of the patient, guidelines established by thehealthcare facility, or the like. For example, the constraint data mayinclude the orthopaedic surgeon's preference for a metal-on-metalinterface, amount of inclination for implantation, the thickness of thebone to resect, size range of the orthopaedic implant, and/or the like.In some embodiments, the orthopaedic surgeon's preferences are saved asa surgeon's profile, which may used as a default constraint values forfurther surgical plans.

In process step 16, the medical images and the constraint data, if any,are transmitted or otherwise provided to an orthopaedic surgicalinstrument vendor or manufacturer. The medical images and the constraintdata may be transmitted to the vendor via electronic means such as anetwork or the like. After the vendor has received the medical imagesand the constraint data, the vendor processes the images in step 18. Theorthopaedic surgical instrument vendor or manufacturer process themedical images to facilitate the determination of the bone cuttingplanes, implant sizing, and fabrication of the customizedpatient-specific orthopaedic surgical instrument as discussed in moredetail below. For example, in process step 20 the vendor may convert orotherwise generate three-dimensional images from the medical images. Forexample, in embodiments wherein the medical images are embodied as anumber of two-dimensional images, the vendor may use a suitable computeralgorithm to generate one or more three-dimensional images form thenumber of two-dimensional images. Additionally, in some embodiments, themedical images may be generated based on an established standard such asthe Digital Imaging and Communications in Medicine (DICOM) standard. Insuch embodiments, an edge-detection, thresholding, watershead, orshape-matching algorithm may be used to convert or reconstruct images toa format acceptable in a computer aided design application or otherimage processing application. Further, in some embodiments, an algorithmmay be used to account for tissue such as cartilage not discernable inthe generated medical images. In such embodiments, any three-dimensionalmodel of the patient-specific instrument (see, e.g., process step 26below) may be modified according to such algorithm to increase the fitand function of the instrument.

In process step 22, the vendor may process the medical images, and/orthe converted/reconstructed images from process step 20, to determine anumber of aspects related to the bony anatomy of the patient such as theanatomical axis of the patient's bones, the mechanical axis of thepatient's bone, other axes and various landmarks, and/or other aspectsof the patient's bony anatomy. To do so, the vendor may use any suitablealgorithm to process the images.

In process step 24, the cutting planes of the patient's bone aredetermined. The planned cutting planes are determined based on the type,size, and position of the orthopaedic prosthesis to be used during theorthopaedic surgical procedure, on the process images such as specificlandmarks identified in the images, and on the constraint data suppliedby the orthopaedic surgeon in process steps 14 and 16. The type and/orsize of the orthopaedic prosthesis may be determined based on thepatient's anatomy and the constraint data. For example, the constraintdata may dictate the type, make, model, size, or other characteristic ofthe orthopaedic prosthesis. The selection of the orthopaedic prosthesismay also be modified based on the medical images such that anorthopaedic prosthesis that is usable with the bony anatomy of thepatient and that matches the constraint data or preferences of theorthopaedic surgeon is selected.

In addition to the type and size of the orthopaedic prosthesis, theplanned location and position of the orthopaedic prosthesis relative tothe patient's bony anatomy is determined To do so, a digital template ofthe selected orthopaedic prosthesis may be overlaid onto one or more ofthe processed medical images. The vendor may use any suitable algorithmto determine a recommended location and orientation of the orthopaedicprosthesis (i.e., the digital template) with respect to the patient'sbone based on the processed medical images (e.g., landmarks of thepatient's bone defined in the images) and/or the constraint data.Additionally, any one or more other aspects of the patient's bonyanatomy may be used to determine the proper positioning of the digitaltemplate.

In some embodiments, the digital template along with surgical alignmentparameters may be presented to the orthopaedic surgeon for approval. Theapproval document may include the implant's rotation with respect tobony landmarks such as the femoral epicondyle, posterior condyles,sulcus groove (Whiteside's line), and the mechanical axis as defined bythe hip, knee, and/or ankle centers.

The planned cutting planes for the patient's bone(s) may then bedetermined based on the determined size, location, and orientation ofthe orthopaedic prosthesis. In addition, other aspects of the patient'sbony anatomy, as determined in process step 22, may be used to determineor adjust the planned cutting planes. For example, the determinedmechanical axis, landmarks, and/or other determined aspects of therelevant bones of the patient may be used to determine the plannedcutting planes.

In process step 26, a model of the customized patient-specificorthopaedic surgical instrument is generated. In some embodiments, themodel is embodied as a three-dimensional rendering of the customizedpatient-specific orthopaedic surgical instrument. In other embodiments,the model may be embodied as a mock-up or fast prototype of thecustomized patient-specific orthopaedic surgical instrument. Theparticular type of orthopaedic surgical instrument to be modeled andfabricated may be determined based on the orthopaedic surgical procedureto be performed, the constraint data, and/or the type of orthopaedicprosthesis to be implanted in the patient. As such, the customizedpatient-specific orthopaedic surgical instrument may be embodied as anytype of orthopaedic surgical instrument for use in the performance of anorthopaedic surgical procedure. For example, the orthopaedic surgicalinstrument may be embodied as a bone-cutting block, a drilling/pinningguide, a milling guide, and/or any other type of orthopaedic surgicaltool or instrument.

The particular shape of the customized patient-specific orthopaedicsurgical instrument is determined based on the planned location of theorthopaedic surgical instrument relative to the patient's bony anatomy.The location of the customized patient-specific orthopaedic surgicalinstrument with respect to the patient's bony anatomy is determinedbased on the type and determined location of the orthopaedic prosthesisto be used during the orthopaedic surgical procedure. That is, theplanned location of the customized patient-specific orthopaedic surgicalinstrument relative to the patient's bony anatomy may be selected basedon, in part, the planned cutting planes of the patient's bone(s) asdetermined in step 24. For example, in embodiments wherein thecustomized patient-specific orthopaedic surgical instrument is embodiedas a drilling/pinning guide (or hereinafter, simply a “pin guide”) foruse in conjunction with a patient-universal cutting block, the locationof the orthopaedic surgical instrument is selected such that the cuttingguide of the patient-universal cutting block, when installed on guidepins placed in the bone by use of the customized patient-specific pinguide, matches one or more of the planned cutting planes determined inprocess step 24. Additionally, the planned location of the orthopaedicsurgical instrument may be based on the identified landmarks of thepatient's bone identified in process step 22.

In some embodiments, the particular shape or configuration of thecustomized patient-specific orthopaedic surgical instrument may bedetermined based on the planned location of the instrument relative tothe patient's bony anatomy. That is, the customized patient-specificorthopaedic surgical instrument may include a bone-contacting surfacehaving a negative contour that matches the contour of a portion of thebony anatomy of the patient such that the orthopaedic surgicalinstrument may be coupled to the bony anatomy of the patient in a uniquelocation, which corresponds to the pre-planned location for theinstrument. When the orthopaedic surgical instrument is coupled to thepatient's bony anatomy in the unique location, one or more guides (e.g.,cutting or drilling guide) of the orthopaedic surgical instrument may bealigned to one or more of the bone cutting plane(s) as discussed above.

One illustrative embodiment of a method 40 for generating a model, suchas a computer model, of a patient-specific orthopaedic instrument isillustrated in FIGS. 2 through 9. The method 40 begins with a step 42 inwhich a cartilage thickness value is determined The cartilage thicknessvalue is indicative of the average thickness of the cartilage of thepatient's bone. As such, in one embodiment, the cartilage thicknessvalue is equal to the average thickness of cartilage for an individualhaving similar characteristics as the patient. For example, thecartilage thickness value may be equal to the average thickness value ofindividuals of the same gender as the patient, the same age as thepatient, having the same activity level of the patient, and/or the like.In other embodiments, the cartilage thickness value is determined basedon one or more medical images of the patient's bone, such as thoseimages transmitted in process step 16.

In step 44, a reference contour of the patient's relevant bone isdetermined. The reference contour is based on the surface contour of athree-dimensional model of the patient's relevant bone, such as thethree-dimensional model generated in step 20. Initially the referencecontour is identical to a region (i.e. the region of interest such asthe distal end of the patient's femur or the proximal end of thepatient's tibia) of the patient's bone. That is, in some embodiments,the reference contour is juxtaposed on the surface contour of the regionof the patient's bone.

Subsequently, in step 46, the reference contour is scaled to compensatefor the cartilage thickness value determined in step 42. To do so, inone embodiment, the scale of the reference contour is increased based onthe cartilage thickness value. For example, the scale of the referencecontour may be increased by an amount equal to or determined from thecartilage thickness value. However, in other embodiments, the referencecontour may be scaled using other techniques designed to scale thereference contour to a size at which the reference contour iscompensated for the thickness of the cartilage on the patient's bone.

For example, in one particular embodiment, the reference contour isscaled by increasing the distance between a fixed reference point and apoint lying on, and defining in part, the reference contour. To do so,in one embodiment, a method 60 for scaling a reference contour asillustrated in FIG. 3 may be used. The method 60 begins with step 62 inwhich a medial/lateral line segment is established on thethree-dimensional model of the patient's relevant bone. Themedial/lateral line segment is defined or otherwise selected so as toextend from a point lying on the medial surface of the patient's bone toa point lying on lateral surface of the patient's bone. The medialsurface point and the lateral surface point may be selected so as todefine the substantially maximum local medial/lateral width of thepatient's bone in some embodiments.

In step 64, an anterior/posterior line segment is established on thethree-dimensional model of the patient's relevant bone. Theanterior/posterior line segment is defined or otherwise selected so asto extend from a point lying on the anterior surface of the patient'sbone to a point lying on posterior surface of the patient's bone. Theanterior surface point and the posterior surface point may be selectedso as to define the substantially maximum local anterior/posterior widthof the patient's bone in some embodiments.

The reference point from which the reference contour will be scaled isdefined in step 66 as the intersection point of the medial/lateral linesegment and anterior/posterior line segment. As such, it should beappreciated that the medial surface point, the lateral surface point,the anterior surface point, and the posterior surface point lie on thesame plane. After the reference point is initially established in step66, the reference point is moved or otherwise translated toward an endof the patient's bone. For example, in embodiments wherein the patient'sbone is embodied as a femur, the reference point is moved inferiorlytoward the distal end of the patient's femur. Conversely, in embodimentswhen the patient's bone is embodied as a tibia, the reference point ismoved superiorly toward the proximal end of the patient's tibia. In oneembodiment, the reference point is moved a distance equal to about halfthe length of the anterior/posterior line segment as determined in step64. However, in other embodiments, the reference point may be movedother distances sufficient to compensate the reference contour forthickness of the cartilage present on the patient's bone.

Once the location of the reference point has been determined in step 68,the distance between the reference point and each point lying on, anddefining in part, the reference contour is increased in step 70. To doso, in one particular embodiment, each point of the reference contour ismoved a distance away from the reference point based on a percentagevalue of the original distance defined between the reference point andthe particular point on the reference contour. For example, in oneembodiment, each point lying on, and defining in part, the referencecontour is moved away from the reference point in by a distance equal toa percentage value of the original distance between the reference pointand the particular point. In one embodiment, the percentage value is inthe range of about five percent to about thirty percent. In oneparticular embodiment, the percentage value is about ten percent.

Referring now to FIGS. 4-9, in another embodiment, the reference contouris scaled by manually selecting a local “high” point on the surfacecontour of the three-dimensional image of the patient's bone. Forexample, in embodiments wherein the relevant patient's bone is embodiedas a tibia as illustrated in FIGS. 4-6, the reference point 90 isinitially located on the tibial plateau high point of the tibial model92. Either side of the tibial plateau may be used. Once the referencepoint 90 is initially established on the tibial plateau high point, thereference point 90 is translated to the approximate center of theplateau as illustrated in FIG. 5 such that the Z-axis defining thereference point is parallel to the mechanical axis of the tibial model92. Subsequently, as illustrated in FIG. 6, the reference point is movedin the distal direction by a predetermined amount. In one particularembodiment, the reference point is moved is the distal direction byabout 20 millimeters, but other distances may be used in otherembodiments. For example, the distance over which the reference point ismoved may be based on the cartilage thickness value in some embodiments.

Conversely, in embodiments wherein the relevant patient's bone isembodied as a femur as illustrated in FIGS. 7-9, the reference point 90is initially located on the most distal point of the distal end of thefemoral model 94. Either condyle of the femoral model 94 may be used invarious embodiments. Once the reference point 90 is initiallyestablished on the most distal point, the reference point 90 istranslated to the approximate center of the distal end of the femoralmodel 94 as illustrated in FIG. 8 such that the Z-axis defining thereference point 90 is parallel to the mechanical axis of the femoralmodel 92. The anterior-posterior width 96 of the distal end of thefemoral model 94 is also determined. Subsequently, as illustrated inFIG. 9, the reference point is moved or otherwise translated in theproximal or superior direction by a distance 98. In one particularembodiment, the reference point is moved in the distal or superiordirection by a distance 98 equal to about half the distance 96. As such,it should be appreciated that one of a number of different techniquesmay be used to define the location of the reference point based on, forexample, the type of bone.

Referring now back to FIG. 2, once the reference contour has been scaledin step 46, the medial/lateral sides of the reference contour areadjusted in step 48. To do so, in one embodiment, the distance betweenthe reference point and each point lying on, and defining in part, themedial side and lateral side of the reference contour is decreased. Forexample, in some embodiments, the distance between the reference pointand the points on the medial and lateral sides of the scaled referencecontour are decreased to the original distance between such points. Assuch, it should be appreciated that the reference contour is offset orotherwise enlarged with respect to the anterior side of the patient'sbone and substantially matches or is otherwise not scaled with respectto the medial and lateral sides of the patient's bone.

The reference contour may also be adjusted in step 48 for areas of thepatient's bone having a reduced thickness of cartilage. Such areas ofreduced cartilage thickness may be determined based on the existence ofbone-on-bone contact as identified in a medical image, simulation, orthe like. Additionally, information indicative of such areas may beprovided by the orthopaedic surgeon based on his/her expertise. If oneor more areas of reduced cartilage thickness are identified, thereference contour corresponding to such areas of the patient's bone isreduced (i.e., scaled back or down).

Additionally, in some embodiments, one or more osteophytes on thepatient's bone may be identified; and the reference contour may becompensated for such presence of the osteophytes. By compensating forsuch osteophytes, the reference contour more closely matches the surfacecontour of the patient's bone. Further, in some embodiments, a distalend (in embodiments wherein the patient's bone is embodied as a tibia)or a proximal end (in embodiments wherein the patient's bone is embodiedas a femur) of the reference contour may be adjusted to increase theconformity of the reference contour to the surface contour of the bone.For example, in embodiments wherein the patient's bone is a femur, thesuperior end of the scaled reference contour may be reduced or otherwisemoved closer to the surface contour of the patient's femur in the regionlocated superiorly to a cartilage demarcation line defined on thepatient's femur. Conversely, in embodiments wherein the patient's boneis embodied as a tibia, an inferior end of the scaled reference contourmay be reduced or otherwise moved closer to the surface contour of thepatient's tibia in the region located inferiorly to a cartilagedemarcation line of the patient's tibia. As such, it should beappreciated that the scaled reference contour is initially enlarged tocompensate for the thickness of the patient's cartilage on the patient'sbone. Portions of the scaled reference contour are then reduced orotherwise moved back to original positions and/or toward the referencepoint in those areas where cartilage is lacking, reduced, or otherwisenot present.

Once the reference contour has been scaled and adjusted in steps 46 and48, the position of the cutting guide is defined in step 50. Inparticular, the position of the cutting guide is defined based on anangle defined between a mechanical axis of the patient's femur and amechanical axis of the patient's tibia. The angle may be determined byestablishing a line segment or ray originating from the proximal end ofthe patient's femur to the distal end of the patient's femur anddefining a second line segment or ray extending from the patient's anklethrough the proximal end of the patient's tibia. The angle defined bythese two line segments/rays is equal to the angle defined between themechanical axis of the patient's femur and tibia. The position of thebone cutting guide is then determined based on the angle between themechanical axes of the patient's femur and tibia. It should beappreciated that, as will be discussed below in more detail, theposition of the cutting guide defines the position and orientation ofthe cutting plane of a patient-universal cutting block when it isinstalled on guide pins placed in the bone by use of a customizedpatient-specific pin guide. Subsequently, in step 52, a negative contourof the customized patient-specific pin guide is defined based on thescaled and adjusted reference contour and the angle defined between themechanical axis of the femur and tibia.

Referring back to FIG. 1, after the model of the customizedpatient-specific orthopaedic surgical instrument has been generated inprocess step 26, the model is validated in process step 28. The modelmay be validated by, for example, analyzing the rendered model whilecoupled to the three-dimensional model of the patient's anatomy toverify the correlation of cutting guides and planes, drilling guides andplanned drill points, and/or the like. Additionally, the model may bevalidated by transmitting or otherwise providing the model generated instep 26 to the orthopaedic surgeon for review. For example, inembodiments wherein the model is a three-dimensional rendered model, themodel along with the three-dimensional images of the patient's relevantbone(s) may be transmitted to the surgeon for review. In embodimentswherein the model is a physical prototype, the model may be shipped tothe orthopaedic surgeon for validation.

After the model has been validated in process step 28, the customizedpatient-specific orthopaedic surgical instrument is fabricated inprocess step 30. The customized patient-specific orthopaedic surgicalinstrument may be fabricated using any suitable fabrication device andmethod. Additionally, the customized patient-specific orthopaedicinstrument may be formed from any suitable material such as a metallicmaterial, a plastic material, or combination thereof depending on, forexample, the intended use of the instrument. The fabricated customizedpatient-specific orthopaedic instrument is subsequently shipped orotherwise provided to the orthopaedic surgeon. The surgeon performs theorthopaedic surgical procedure in process step 32 using the customizedpatient-specific orthopaedic surgical instrument. As discussed above,because the orthopaedic surgeon does not need to determine the properlocation of the orthopaedic surgical instrument intra-operatively, whichtypically requires some amount of estimation on part of the surgeon, theguesswork and/or intra-operative decision-making on part of theorthopaedic surgeon is reduced.

Referring now to FIGS. 10-12, in one embodiment, the customizedpatient-specific orthopaedic surgical instrument may be embodied as atibial pin guide 100. The pin guide 100 is configured to be coupled to atibia of a patient. As will be described below in greater detail, thetibial pin guide 100 is used to install a pair of guide pins 160 in alocation on the tibia of the patient that has been customized for thatparticular patient. However, the tibial pin guide 100 is devoid of acutting guide. As a result, once the tibial pin guide 100 has been usedto install the guide pins 160, it is removed from the patient's tibiaand a patient-universal cutting block 162 (see FIG. 20) is installed onthe guide pins 160 and thereafter used to resect the patient's tibia.This is in contrast to the fabrication and use of a customizedpatient-specific cutting block. Such an arrangement allows for a certaindegree of customization of the surgical procedure by customizing theplacement of the guide pins 160 to the patient's anatomy, while alsoenjoying the cost benefits associated with the use of a reusablepatient-universal cutting block.

The pin guide 100 includes a body 102 configured to be coupled to theanterior side of the patient's tibia and two arms or tabs 104, 106 whichextend posteriorly away from the body 102. The tabs 104, 106 areconfigured to wrap around a proximal end of the tibia as discussed inmore detail below. The pin guide 100 may be formed from any suitablematerial. For example, the pin guide 100 may be formed from a plastic orresin material. In one particular embodiment, the pin guide 100 isformed from Vero resin using a rapid prototype fabrication process.However, the pin guide 100 may be formed from other materials in otherembodiments. For example, in another particular embodiment, the pinguide 100 is formed from a polyimide thermoplastic resin, such as aUltem resin, which is commercially available from Saudi Basic IndustriesCorporation Innovative Plastics of Riyhadh, Saudi Arabia. In theillustrative embodiment described herein, the pin guide 100 is formed asa monolithic polymer structure.

The body 102 of the pin guide 100 includes a bone-contacting orbone-facing surface 112 and an outer surface 114 opposite thebone-facing surface 112. The body 102 has a number of guide holes 116defined therethrough. A removable drill bushing 118 is locked into eachguide hole 116. As will be described below in greater detail, theremovable drill bushings 118 may be installed in the pin guide 100 foruse in a surgical procedure and then removed from the pin guide 100after the procedure. Whereas the pin guide 10 is customized componentthat is disposed of after its single use on the patient for which it wasmade, the removed drill bushings 118 may be sterilized and reused in asubsequent surgical procedure.

The bone-facing surface 112 of the pin guide's body 102 includes anegative contour 138 configured to receive a portion of the anteriorside of the patient's tibia having a corresponding contour and,optionally, a portion of the medial side of the patient's tibia. Thecustomized patient-specific negative contour 138 of the bone-contactingsurface 112 allows the positioning of the pin guide 100 on the patient'stibia in a unique pre-determined location and orientation. In theexemplary embodiment described herein, the negative contour 138 isselected such that the pin guide 100 is configured to be coupled to thepatient's tibia on an anterior surface of the tibia, although it mayalso be configured to be coupled to the anterior-medial side of thepatient's tibia.

The tabs 104, 106 include a bone-contacting or bone-facing surface 140,142, respectively, and an outer surface 144, 146, respectively, oppositethe bone-facing surface 140, 142. The bone-facing surface 140 of the tab104 includes a negative contour 148 configured to receive a portion ofthe proximal side of the patient's tibia having a respectivecorresponding contour. Similarly, the bone-facing surface 142 of the tab106 includes a negative contour 150 configured to receive a portion ofthe proximal side of the patient's tibia having a respectivecorresponding contour.

As discussed above, the arms or tabs 104, 106 extend posteriorly fromthe body 102 to define a U-shaped opening therebetween. The tabs 104,106 may extend from the body 102 the same distance or a differentdistance. Moreover, as shown in FIG. 11. the tabs 104, 106 may extendposteriorly at a non-parallel angle relative to one another.

In some embodiments, the negative contours 138, 148, 150 of thebone-contacting surfaces 112, 140, 142 of the customizedpatient-specific pin guide 100 may or may not match the correspondingcontour surface of the patient's bone. That is, as discussed above, thenegative contours 138, 148, 150 may be scaled or otherwise resized(e.g., enlarged) to compensate for the patient's cartilage or lackthereof.

As can be seen in FIGS. 13-15, the removable drill bushing 118 includesa head 120 that is contoured to be gripped by a surgeon's fingers. Apost 122 extends away from the head 120 and includes a locking flange124 formed on the outer surface thereof. The locking flange 124 isutilized to lock the post 122 within one of the guide holes 116 of thepin guide 100. Specifically, a locking slot 126 is formed in the pinguide's body 102 proximate to each of the guide holes 116. The lockingslots 126 extend in a direction parallel to the axis of each of therespective guide holes 116 and open into the guide holes 116. In theillustrative embodiment of FIGS. 10-15, the locking flanges 124 of theremovable drill bushings 118 are embodied as a number of male threads124 extending helically around the outer surface of the post 122, withthe locking slots 126 of the pin guide 100 being embodied as a number offemale threads 126 extending helically around the periphery of each ofthe guide holes 116. The drill bushing's male threads 124 are sized tothread into the female threads 126 formed in the guide holes 116 of thepin guide 100.

An elongated bore 128 extends through the removable drill bushing 118.The bore 128 is sized to receive a drill such that the patient's tibiamay be pre-drilled prior to installation of the guide pins 160. As shownin FIG. 15, each end of the bore 128 is countersunk. The countersunkopening on the drill bushing's head 120 functions as a lead-in tofacilitation insertion of the drill and the guide pins 160 into the bore128.

The removable drill bushings 118 may be provided to the surgeonseparately from the pin guide 100. In particular, one or more of theremovable drill bushings 118 may be provided to the surgeon in aseparate sterile package from the sterile package that includes the pinguide 100. Unlike the pin guide 100 that is designed as a single-usedisposable component, the removable drill bushings may be sterilized andreused after each procedure. As such, additional drill bushings 118 maynot be needed each time a new pin guide 100 is procured by the surgeon.

The removable drill bushings 118 may be constructed from a medical-grademetal such as stainless steel, cobalt chrome, or titanium, althoughother metals or alloys may be used.

As shown in FIGS. 16-20, a surgeon may use the customizedpatient-specific tibial pin guide 100 to install a pair of guide pins160 in locations on the tibia of the patient that have been customizedfor that particular patient. A patient-universal cutting block 162 maythen be installed on the custom-located guide pins 160 and thereafterused to resect the patient's tibia. Such an arrangement allows for acertain degree of customization of the surgical procedure by customizingthe placement of the guide pins 160 to the patient's anatomy, while alsoenjoying the cost benefits associated with use of the reusablepatient-universal cutting block 162.

As shown in FIG. 16, the surgical procedure commences with assembly ofthe customized patient-specific surgical instrument on a prep table orother part of the surgery room. To do so, the surgeon first obtains acustomized patient-specific pin guide 100 that was fabricated for theparticular patient being treated by the surgeon. The pin guide 100 isfabricated in the manner described above in regard to FIGS. 1-9. Oncethe customized patient-specific pin guide 100 has been obtained, thesurgeon then takes a pair of the sterilized removable drill bushings 118and installs them to the pin guide 100. In particular, the surgeonobtains a pair of the removable drill bushings 118 from a previousprocedure (after being sterilized) or new drill bushings 118 (from themanufacturer's sterilized packaging). Thereafter, the surgeon insertsthe threaded post 122 of one of the drill bushings 118 into one of theguide holes 116 formed in the pin guide 100 and rotates the head 120 ofthe drill bushing 118 so that the external threads 124 formed on theouter surface of the post 122 are threaded into the female threads 126formed in the guide hole 116. The surgeon then obtains the other drillbushing 118 and installs it in the pin guide's other guide hole 116 in asimilar manner.

As shown in FIG. 17, the assembled customized patient-specific pin guide100 is then coupled to the proximal end of the patient's tibia. Becausethe bone-contacting surfaces 112, 140, 142 of the pin guide 100 includethe negative contours 138, 148, 150, the pin guide 100 is coupled to thepatient's tibia in a pre-planned, unique position. When so coupled, thetabs 104, 106 wrap around the proximal end of the patient's tibia, andthe elongated bores 128 of the drill bushings 118 extend in theanterior/posterior direction away from the anterior surface of thepatient's tibia.

The surgeon then installs the guide pins 160. To do so, the surgeonfirst drills pilot holes in the patient's tibia by advancing a drill(not shown) through the guide bore 128 of each of the drill bushings118. The surgeon then inserts a guide pin 160 through the guide bore 128of each of the drill bushings 118 and into the drilled pilot holes. Assuch, the guide pins 160 are installed in the patient's tibia incustomized, patient-specific locations created by use of the customized,patient-specific pin guide 100. It should be appreciated that if theguide pins 160 are self-tapping pins, pre-drilling of the patient'stibia is not necessary.

As shown in FIG. 18, once the guide pins 160 are installed in thepatient's tibia in the customized, patient-specific locations by use ofthe pin guide 100, the drill bushings 118 are removed. Specifically, thesurgeon first grips the head 120 of one of the drill bushings 118 androtates it in the opposite direction it was rotated during installation(e.g., counterclockwise) such that the external threads 124 formed onthe outer surface of the drill bushing's post 122 are unthreaded fromthe female threads 126 formed in the guide hole 116. Once unthreaded,the drill bushing 118 may be lifted away from the pin guide 100. Thesurgeon then removes the other drill bushing 118 from the pin guide'sother guide hole 116 in a similar manner The drill bushings 118 are notdisposed of, but rather may be retained and sterilized for use in asubsequent surgical procedure in combination with a customizedpatient-specific pin guide 100 that has been fabricated for anotherpatient.

As shown in FIG. 19, with the drill bushings 118 removed, the pin guide100 is then de-coupled and removed from the patient's tibia. In doingso, the guide pins 160 are left behind in the patient's tibia in thecustomized, patient-specific locations created by use of the pin guide100. As shown in FIG. 20, the patient-universal cutting block 162 isthen used to resect the patient's tibia in the desired location andorientation. The patient-universal cutting block 162 includes a cuttingguide 164 that, in the illustrative embodiment described herein, is inthe form of a cutting slot 166 formed in the cutting block's body 168.The body 168 of the patient-universal cutting block 162 also hasmultiple pairs of guide pin holes formed therein. For example, in theillustrative embodiment described herein, the cutting block's body 168has three different corresponding pairs of guide pin holes 170, 172, and174. As will be described below in greater detail, the patient-universalcutting block 162 may be selectively positioned on the guide pins 160 byuse of the guide pin holes 170, 172, and 174 to alter the position ofthe cutting slot 166 and hence the amount of bone removed duringresection. For example, in FIG. 20, the cutting block is positioned inthe pair of guide pin holes 170 corresponding to the baseline or “zero”setting. If the surgeon desires to take off more bone (e.g., +2 mm) thanwould otherwise be removed by use of the zero setting, the surgeon canremove the patient-universal cutting block 162 from the guide pins 160and reinstall it such that the guide pins 160 are received into theguide pin holes 172. Conversely, if the surgeon desires to take off lessbone (e.g., −2 mm) than would otherwise be removed by use of the zerosetting, the surgeon can remove the patient-universal cutting block 162from the guide pins 160 and reinstall it such that the guide pins 160are received into the guide pin holes 174.

As shown in FIG. 20, once the patient-universal cutting block 162 hasbeen installed with use of the desired pair of guide pin holes (in theillustrative example of FIG. 20, the guide pin holes 170), the surgeonmay use the patient-universal cutting block to resect the proximal endof the patient's tibia. To do so, the surgeon advances a bone saw bladeinto the cutting slot 166 and cuts the tibia. If need be, the surgeonmay then reposition the cutting block 162 with use of a different pairof guide pin holes to perform a second cut to remove more bone. Once thepatient's proximal tibia has been resected, the surgeon may thencontinue with the surgical procedure.

Referring now to FIGS. 21-23, the customized patient-specificinstruments described herein may also be embodied as a customizepatient-specific femoral pin guide 200. The pin guide 200 is configuredto be coupled to the femur of a patient. The pin guide 200 includes abody 202 configured to be coupled to the anterior side of the patient'sfemur and two arms or tabs 204, 206, which extend posteriorly away fromthe body 202. The tabs 204, 206 are configured to wrap around a distalend of the femur. Each of the tabs 204, 206 includes an inwardly-curvingor otherwise superiorly extending lip 208, 210.

Like the tibial pin guide 100, the femoral pin guide 200 may be formedfrom a material such as a plastic or resin material. In someembodiments, the pin guide 200 may be formed from a photo-curable orlaser-curable resin. In one particular embodiment, the pin guide 200 isformed from a Vero resin using a rapid prototype fabrication process.However, the pin guide 200 may be formed from other materials in otherembodiments. For example, in another particular embodiment, the pinguide 200 is formed from a polyimide thermoplastic resin, such as aUltem resin. In the illustrative emobodiment described herein, the pinguide 200 is embodied as a monolithic structure.

The body 202 includes a bone-contacting or bone-facing surface 212 andan outer surface 214 opposite the bone-facing surface 212. The body 202has a number of threaded guide holes 216 defined therethrough. One ofthe removable drill bushings 118 may be threaded into each of the guideholes 216. In addition to the guide holes 216 formed in the pin guide'sbody 202, another pair of guide holes 216 is formed in the tabs 204,206. Similarly to as described above in regard to the tibial pin guide100, the removable drill bushings 118 may be installed in the femoralpin guide 200 for use in a surgical procedure and then removed from thepin guide 200 after the procedure. Like the tibial pin guide 100, thefemoral pin guide 200 is a customized component that is disposed ofafter its single use on the patient for which it was made.

The bone-facing surface 212 of the femoral pin guide's body 202 includesa negative contour 228 configured to receive a portion of the anteriorside of the patient's femur having a corresponding contour. As discussedabove, the customized patient-specific negative contour 228 of thebone-contacting surface 212 allows the positioning of the pin guide 200on the patient's femur in a unique pre-determined location andorientation.

As alluded to above, the arms or tabs 204, 206 extend posteriorly fromthe body 202 to define a somewhat U-shaped opening therebetween. Thetabs 204, 206 may extend from the body 202 the same distance or adifferent distance. Each of the tabs 204, 206 has a threaded guide hole216 formed therein. One of the removable drill bushings 118 may bethreaded into each guide hole 216 of the tabs 204, 206. In particular,the guide holes 216 of the tabs 204, 206 have a similar diameter andconfiguration as the guide holes 216 of the pin guide's body 202 and theguide holes 116 of the tibial pin guide 100. As such, the removabledrill bushings 118 are interchangeable between the tibial pin guide 100and the femoral pin guide 200.

The tabs 204, 206 include a bone-contacting or bone-facing surface 240,242, respectively, and an outer surface 244, 246, respectively, oppositethe bone-facing surface 240, 242. The bone-facing surface 240 of the tab204 includes a negative contour 248 configured to receive a portion ofthe distal side of the patient's femur having a respective correspondingcontour. Similarly, the bone-facing surface 242 of the tab 206 includesa negative contour 250 configured to receive a portion of the distalside of the patient's femur having a respective corresponding contour.

In some embodiments, the negative contours 228, 248, 250 of thebone-contacting surfaces 212, 240, 242 of the customizedpatient-specific pin guide 200 may or may not match the correspondingcontour surface of the patient's bone. That is, as discussed above, thenegative contours 228, 248, 250 may be scaled or otherwise resized(e.g., enlarged) to compensate for the patient's cartilage or lackthereof.

As shown in FIG. 23, the femoral pin guide 200 may be coupled to thedistal end of the patient's femur. Because the bone-contacting surfaces212, 240, and 242 of the pin guide 200 include the negative contours228, 248, 250, the femoral pin guide may be coupled to the patient'sfemur in a pre-planned, unique position. When so coupled, the tabs 204,206 wrap around the distal end of the patient's femur. Additionally,when the femoral pin guide 200 is coupled to the patient's femur, aportion of the anterior side of the femur is received in the negativecontour 228 of the body 202 and a portion of the distal side of thepatient's femur is received in the negative contours 248, 250 of thetabs 204, 206, respectively.

Once coupled to the patient's distal femur, a surgeon may use thecustomized patient-specific femoral pin guide 200 to install two pairsof guide pins 160 in locations that have been customized for thatparticular patient. One pair of the guide pins 160 is installed in acustom patient-specific location on the anterior side of the patient'sfemur. The other pair of guide pins 160 is installed on the distal sideof the patient's femur. With the pin guide 200 removed, apatient-universal cutting block or blocks (not shown) may then beinstalled on the custom-located guide pins 160 and thereafter used toresect the patient's femur. Such an arrangement allows for a certaindegree of customization of the surgical procedure by customizing theplacement of the guide pins 160 to the patient's anatomy, while alsoenjoying the cost benefits associated with the use of a reusablepatient-universal cutting block(s).

Referring now to FIGS. 24-27, there is shown another embodiment of thepin guide 100 and the removable drill bushing 118. The pin guide 100 andthe drill bushing 118 shown in FIGS. 24-27 are essentially the same asthe pin guide 100 and the drill bushing 118 shown in FIGS. 10-20 withthe exception of the locking mechanism that locks the removable drillbushing 118 within the guide holes 116 of the pin guide 100. Inparticular, in lieu of locking threads, in the illustrative embodimentof the pin guide 100 and the removable drill bushing 118 shown in FIGS.24-27 utilizes a cam lock arrangement.

As shown in FIGS. 24 and 25, the locking slot 126 formed in the pinguide's body 102 proximate to each of the guide holes 116 is nothelical, but rather includes two elongated channels 180 positioned onopposite sides of the guide hole 116 and an annular recess 182 formedwithin the pin guide's body 102. The outer ends of the channels 118 opento the outer surface 114 of the guide pin's body 102, with the innerends of the channels 180 opening into the annular recess 182. As can beseen in the cross sectional view of FIG. 25, a shoulder 184 defines theanterior side of the locking slot's annular recess 182. As can also beseen in FIG. 25, the shoulder 184 is embodied as an angled cam surface.As will be described below, the locking flange 124 of the removabledrill busing engages the cam surface to lock the removable drill bushing118 to the pin guide 100.

The locking flange 124 of the removable drill bushing 118 of FIGS. 26and 27 is embodied as a pair of tabs extending outwardly from oppositesides of its post 122. The tabs 124 are sized and positioned to bereceived into the respective channels 180 of the pin guide's lockingslot 126. Specifically, to lock the removable drill bushing 118 to thepin guide 100, each of the tabs 124 is first aligned with one of thechannels 180 and thereafter advanced into the channels 180. When thetabs 124 have been advanced into the channels 180 far enough to clearthe shoulder 184, the head 120 of the removable drill bushing 118 may berotated approximately 90° thereby also rotating the tabs 124. Suchrotation of the tabs 124 removes the tabs from alignment with thechannels 180 thereby capturing the tabs 124 within the annular recess182. Such rotation also causes the anterior cam surface 186 of the tabs124 to engage the cam surface of the shoulder 184. This cam locks theremovable drill bushing 118 to the drill guide 100.

To unlock the removable drill bushing 118 from the drill guide 100, thehead 120 of the removable drill bushing 118 may be rotated in theopposite direction it was rotated during installation to a position inwhich the tabs 124 are aligned with the channels 180. Once the tabs 124are aligned in such a manner, the post 122 of the removable drillbushing 118 may be slid out of the guide hole 116 thereby disassemblingthe removable drill bushing 118 from the pin guide 100.

It should be appreciated that although the locking mechanism of FIGS.24-27 is illustratively described within the context of the tibial pinguide 100, the femoral pin guide 200 may also be modified to includesuch a cam lock arrangement in lieu of the threaded arrangementdescribed above in regard to FIGS. 21-23.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arisingfrom the various features of the apparatus, system, and method describedherein. It will be noted that alternative embodiments of the apparatus,system, and method of the present disclosure may not include all of thefeatures described yet still benefit from at least some of theadvantages of such features. Those of ordinary skill in the art mayreadily devise their own implementations of the apparatus, system, andmethod that incorporate one or more of the features of the presentinvention and fall within the spirit and scope of the present disclosureas defined by the appended claims.

What is claimed is:
 1. A method of performing an orthopaedic surgicalprocedure on a bone of a patient, comprising: assembling a customizedpatient-specific pin guide assembly by (i) locking a first removabledrill bushing into a first hole of a customized patient-specific pinguide, and (ii) locking a second removable drill bushing into a secondhole of the customized patient-specific pin guide, positioning theassembled customized patient-specific pin guide assembly in contact withthe bone of the patient, inserting a pair of guide pins into the bone ofthe patient by (i) advancing a first guide pin of the pair of guide pinsthrough the first removable drill bushing, and (ii) advancing a secondguide pin of the pair of guide pins through the second removable drillbushing, removing the customized patient-specific pin guide assemblyfrom the bone of the patient without removing the pair of guide pinsfrom the bone of the patient, positioning a patient-universal cuttingblock into contact with the bone of the patient such that the pair ofguide pins is received into a pair of guide pin holes defined in thepatient-universal cutting block, and making a cut in the bone of thepatient with the patient-universal cutting block.
 2. The method of claim1, wherein removing the customized patient-specific pin guide assemblyfrom the bone of the patient comprises: disassembling the customizedpatient-specific pin guide assembly by (i) unlocking the first removabledrill bushing from the first hole of the customized patient-specific pinguide, and (ii) unlocking the second removable drill bushing from thesecond hole of the customized patient-specific pin guide, and removingthe disassembled customized patient-specific pin guide assembly from thebone of the patient without removing the pair of guide pins from thebone of the patient.
 3. The method of claim 1, further comprising:removing the patient-universal cutting block from the bone of thepatient prior to making the cut in the bone of the patient, andrepositioning the patient-universal cutting block into contact with thebone of the patient such that the pair of guide pins is received into asecond, different pair of guide pin holes defined in thepatient-universal cutting block prior to making the cut in the bone ofthe patient.
 4. The method of claim 3, wherein repositioning thepatient-universal cutting block into contact with the bone of thepatient comprises: determining an amount of bone to be removed from thebone of the patient subsequent to positioning the patient-universalcutting block into contact with the bone of the patient, selecting thepair of second, different guide pin holes which corresponds to theamount of bone to be removed from the bone of the patient from aplurality of pairs of guide pin holes, and repositioning thepatient-universal cutting block into contact with the bone of thepatient such that the pair of guide pins is received into the selectedsecond, different pair of guide pin holes defined in thepatient-universal cutting block prior to making the cut in the bone ofthe patient.
 5. The method of claim 1, wherein: positioning theassembled customized patient-specific pin guide assembly in contact withthe bone of the patient comprises positioning the assembled customizedpatient-specific pin guide assembly in contact with a femur of thepatient, and making the cut in the bone of the patient with thepatient-universal cutting block comprises making the cut in the femur ofthe patient with the patient-universal cutting block.
 6. The method ofclaim 1, wherein: positioning the assembled customized patient-specificpin guide assembly in contact with the bone of the patient comprisespositioning the assembled customized patient-specific pin guide assemblyin contact with a tibia of the patient, and making the cut in the boneof the patient with the patient-universal cutting block comprises makingthe cut in the tibia of the patient with the patient-universal cuttingblock.